During the Jack the Ripper murders, Warren, who was the Commissioner of the London Metropolitan Police, erased from a wall near one of the killings, masonic code words concerning the "Juwes" or "Three Unworthy Craftsmen," who in masonic lore, are the fabled assassins of Hiram of Tyre, “the Widow’s Son” — legendary architect of the Temple of Solomon. The words were evidence suggesting that the Ripper was a Freemason, or someone familiar with what were closely guarded masonic secrets at the time.

Though he has been heavily criticized for alleged mistakes in his research, the late author Stephen Knight remains one of the best sources on the masonic nature of the Jack the Ripper killings in his indispensable book, "Jack the Ripper: The Final Solution.” Another valuable source is the graphic book From Hellby Alan Moore.